Battle lines drawn as Britain squares up for EU vote

Campaigning in Britain's Brexit referendum officially begins on Friday, ten weeks ahead of a vote that will hand Britons their first chance to have their say on Europe since 1975.

With opinion polls suggesting the British public are deeply divided on whether to stay in the EU, the Leave campaign's biggest name -- charismatic London mayor Boris Johnson -- will lead its "Brexit blitz" with rallies on Friday and Saturday in three northern cities.

Johnson, who is seeking to persuade the British people that they could thrive if cut free from EU red tape, has compared leaving the bloc to escaping from prison, saying the referendum was "like the jailor has accidentally left the door of the jail open and people can see the sunlit lands beyond".

In the "Remain" corner is Prime Minister David Cameron, who says Britain has a "special status" within the EU thanks to a renegotiation he sealed in February, and that the country will be richer and stronger if it stays in.

He is confident of winning the June 23 poll, despite deep divisions within his Conservative party on Europe and recent difficulties over a controversial budget, threats to Britain's steel industry and the so-called Panama Papers leak.

His "Britain Stronger In Europe" campaign has drawn support from the country's main political parties and some of its biggest employers.

International bodies such as the International Monetary Fund (IMF) have also warned that a Brexit could damage Britain.

Debate about whether Britain should stay in the EU has been raging for weeks, but the race shifted up a gear this week when the two official campaigns were crowned by election officials.

This unlocked a treasure chest of publicly-funded benefits for both sides to ramp up their campaigns, as well as removing the ambiguity about who will be the major faces seeking to persuade Britons either way.

- 'Gun to a knife fight' -

The Vote Leave campaign beat the Leave.EU campaign supported by UK Independence Party leader Nigel Farage to be named the official Brexit campaign by election officials on Wednesday.

The threat of a legal challenge to the decision by Leave.EU has been withdrawn.

Opinion polls indicate the referendum -- which has so far centred on the economy and immigration, but which few voters outside Westminster have engaged with -- will be tight.

The "Remain" and "Leave" camps are level on 50 percent support, according to a poll of polls run by academics at the What UK Thinks project.

Jeremy Corbyn, leader of the main opposition Labour, only made his first big pro-EU speech Thursday and previously opposed EU membership but could play a key role in engaging voters, particularly the young.

"It is a good rule in politics to always take a gun to a knife fight," wrote former Labour advisor John McTernan in the Daily Telegraph Thursday.

"Currently Labour, and 'Remain', are taking deckchairs. That has to end."

Voters are also increasingly distrustful of what Cameron tells them about the referendum, YouGov polling for The Times suggested this week, as the government started sending millions of pro-EU leaflets to British homes.

It found that only 21 percent of people trusted his statements and claims on the issue, down eight percentage points in two months.

Turnout is likely to be key in determining the outcome, experts believe.

"Such evidence as we do have consistently points to 'Leave' voters reporting on being keener to make it to the polls," said John Curtice of Strathclyde University, Britain's leading poll expert.

"Leave" campaigners took heart from the fact that only 32 percent of people in the Netherlands voted in last week's referendum on an EU deal with Ukraine, seen as linked to anti-Brussels sentiment.

For their part, the "Remain" camp this week launched a YouTube campaign called "Talk To Gran" urging young people to persuade their grandparents to vote for continued EU membership.